Kerckring's center for ossification is one of the variant of skull anatomy which is associated with:

Kerckring's ossification center or bone is the area that undergoes cailaginous ossification at the posterior margin of the foramen magnum before it fuses early in life with the occipital bone. Other accessory bones of the skull:Sutural bones (wormian bones) are most often seen at fontanelles and at the junction of two or more sutures, especially in the region of the lambdoid suture.A prominent sutural bone at the lambda (a junction at the lambdoid and sagittal sutures) is referred as Inca bone or Gahe's ossicles.The epipteric bones or pterion ossicles are sutural bones that are sometimes seen at the pterion of the skull.Other unnamed accessory bones or ossification centers are occasionally seen (e.g., skull base accessory ossification centers).